University of Maryland Extension

Bacterial Leaf Scorch - Trees

Bacterial leaf scorch
Bacterial leaf scorch on oak tree - credit: J. Sherald US Dept. Interior, NPS

Bacterial leaf scorch is a disease of shade trees in Maryland. It affects a large number of shade trees including elm, catalpa, hackberry, gingko, oak, sycamore, maple, mulberry, and sweetgum in the landscape. Depending on the severity, this disease can cause tree death. 

The pathogen is a bacterium that grows inside the plant’s vascular tissue where it blocks water movement from the roots.  The organism, Xylella fastidiosa, is a small gram Leaf scorchnegative bacterium with no flagella.  It doesn’t form resting spores, has a thick rippled cell wall, and does not grow on conventional bacteriological media.  This bacterium is spread by plant hoppers called sharpshooters, treehoppers and spittlebugs that feed on infected plants and after feeding, the bacterium will spread systemically through the vascular system. Symptoms typically appear in mid to late summer on lower branches as irregular marginal browning on interior leaves. Symptoms progress along the branch towards the tip.
Symptoms will occur every year and progress through the crown. Scorched areas may have a yellow halo around them depending on the tree species. Reduced growth and dieback are also common in severely infected plants. These symptoms are sometimes mistaken for drought, environmental stress, or root diseases.  
Bacterial scorch symptoms differ from drought scorch symptoms, in that they appear first on the lower branches and on the older interior leaves. Drought scorch symptoms will be more uniform and will first appear near the upper branches and on the younger leaves near the tips of the branches.

bacterial leaf scorch on elm
Bacterial leaf scorch symptoms on elm

bacterial leaf scorch on sycamore
Bacterial leaf scorch symptoms on sycamore

bacterial leaf scorch on maple
Bacterial leaf scorch symptoms on maple leaves


Management of bacterial leaf scorch

There are no treatments for bacterial leaf scorch. However, infected trees may continue to persist in the landscape if symptomatic branches and dead wood is pruned out promptly. Antibiotic trunk injections have shown promise but they only relieve symptoms and don’t provide a cure.

Additional Resource

Bacterial Leaf Scorch  (PDF)

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